An attempt to independently verify the utility of the Van Nuys Prognostic Index for ductal carcinoma in situ

Abstract

The Van Nuys Prognostic Index (VNPI) purports to predict the risk of ipsilateral breast tumor recurrence (IBTR) after excision of ductal carcinoma in situ (DCIS). It is a simple scoring scheme based on a retrospective evaluation of data from a single group of investigators. Various versions of VNPI have been proposed using clinical and pathologic features including tumor size, tumor grade, margin width, and patient age. Despite common use of VNPI in the clinical management of patients with DCIS, independent validation is lacking. A total of 222 patients were retrospectively analyzed with mammographically detected DCIS who were treated with surgical excision alone. Wire-localized excisional biopsy was performed and surgical specimens were measured and inked to assist in margin assessment. Multiple sections of each specimen were evaluated for histopathologic subtype, histologic and nuclear grade, presence of necrosis, maximum dimension of the lesion, and margin width. Each patient was prospectively evaluated by a multidisciplinary management team and presented with adjuvant treatment options including whole breast radiotherapy and/or tamoxifen. All patients in this cohort declined radiotherapy. Thirty-one percent of patients received tamoxifen. Patients were followed clinically every 3 to 6 months, and mammographically every 6 to 12 months. IBTR was confirmed by biopsy. Wilcoxon regression analysis was used to evaluate risk groups according to 3 proposed VNPI classification schemes: VNPI Group 1 (margin, grade, and size), VNPI Group 2 (margin, grade, size, and patient age), and VNPI Group 3 (margin only). With a median follow-up of 4.6 years, the crude rate of IBTR was 8.6% for the entire cohort. Of the patients who developed an IBTR, 73.7% had a lesion with a maximum dimension of < or =15 mm, 47.4% had a margin > or =10 mm, and 36.8% had grade 1 histology. At 5 years, IBTR was statistically indistinguishable for the 3 VNPI models. The 5-year freedom from IBTR for low-risk, intermediate-risk, and high-risk groups according to VNPI Group 1 was 96%, 84%, and 100%, respectively (P = .20). Similarly, the 5-year freedom from IBTR for low-risk, intermediate-risk, and high-risk groups according to VNPI Group 2 was 95%, 83%, and 100%, respectively (P = .19). Taking into account margin status only (VNPI Group 3) the 5-year freedom from IBTR for low-risk, intermediate-risk, and high-risk groups was 92%, 91%, and 91%, respectively (P = .98). Tamoxifen use did not appear to affect the 5-year rate of IBTR (95% vs 94%; P = 1.0). The results of the current study suggest that VNPI or margin width alone is not a valid tool with which to assist in the stratification of patients after excision alone for their risk of IBTR at 5 years. Further follow-up may strengthen the predictive utility of the various VNPI classification schemes.